The present invention relates to junction field effect transistors (JFETs) having structures suitable for integration in bipolar ICs.
The junction field effect transistors are widely used in input stages of amplifiers because of their low noise performance.
Japanese patent provisional publication No. 57-211278 shows a conventional type junction field effect transistor integrated in a bipolar IC.
As mentioned later with reference to FIGS. 4 and 5, the junction field effect transistor of this conventional example is unsatisfactory in that a drain saturation current Idss is unknown at the time of initial design and layout of an IC.